Transference numbers of electrons

Some of the materials recently being considered for use as positive electrodes, such as LiFeP04, are actually insulators rather than electronic conductors. In this case, the assumption that the transference number of electrons is unity is not valid, and semiconducting effects may need to be... 

When the e.m.f. of a cell is measured by balancing it against an external voltage, so that no current flows, the maximum e.m.f. is obtained since the cell is at equilibrium. The maximum work obtainable from the cell is then nFE J, where n is the number of electrons transferred, F is the Faraday unit and E is the maximum cell e.m.f. We saw in Chapter 3 that the maximum amount of work obtainable from a reaction is given by the free energy change, i.e. - AG. Hence... 

In the previous section we saw how voltammetry can be used to determine the concentration of an analyte. Voltammetry also can be used to obtain additional information, including verifying electrochemical reversibility, determining the number of electrons transferred in a redox reaction, and determining equilibrium constants for coupled chemical reactions. Our discussion of these applications is limited to the use of voltammetric techniques that give limiting currents, although other voltammetric techniques also can be used to obtain the same information. 

When the discharge has been set up, there is a movement of electrons from cathode to anode and a corresponding movement of positive ions from the anode to cathode. These transfers of electrons and ions to each electrode must balance to maintain electrical neutrality in the circuit. Thus, the number of positive ions discharging at the cathode must equal the number of electrons discharging at the anode. This occurs, but the actual drift velocities of electrons and ions toward the respective electrodes are not equal. 

Table 1. Transference Number of Cations, Anions t, and Electrons or Holes in Several Compounds...

A substantial number of photo-induced charge transfer polymerizations have been known to proceed through N-vinylcarbazole (VCZ) as an electron-donor monomer, but much less attention was paid to the polymerization of acrylic monomer as an electron receptor in the presence of amine as donor. The photo-induced charge-transfer polymerization of electron-attracting monomers, such as methyl acrylate(MA) and acrylonitrile (AN), have been recently studied [4]. In this paper, some results of our research on the reaction mechanism of vinyl polymerization with amine in redox and photo-induced charge transfer initiation systems are reviewed. 

Figure 2. The average number of electron charges transferred from Zn atoms to Cu atoms in fee disordered alloys. The solid dots are calculated with the LSMS. The open circles are obtained using the CPA-LSMS. The squares are obtained using the SCF-KKR-CPA.

Suppose, for example, that the conductor A initially bears a negative charge on its surface—that is to say, a certain number of electrons are distributed over its surface. When the whole of this charge has been transferred to the smaller sphere B, the same number of electrons are distributed over a small surface area the average distance between the electrons is smaller than before to Fiu j5... 

Electrical Conduction by Proton Jumps. As mentioned in Sec. 24, a hydroxyl ion may be regarded as a doubly charged oxygen ion 0 , containing a proton inside the electronic cloud of the ion, which has the same number of electrons as a fluoride ion. The radius of the hydroxyl ion cannot be very different from that of the fluoride ion. But it will be seen from Table 2 that the mobility of the hydroxyl ion is about four times as great. This arises from the fact that a large part of the mobility is undoubtedly due to proton transfers.1 Consider a water molecule in contact with a hydroxyl ion. If a proton jumps from the molecule to the ion,... 

The approach used in Example 18.5 to find the number of moles of electrons transferred, n, is generally useful. What you do is to break down the equation for the cell reaction into two half-equations, oxidation and reduction. The quantity n is the number of electrons appearing in either half-equation. 

See also Oxidation, Reduction). Some dissolved substances in water occur either in an oxidized or a reduced form, and their state can be changed by either the acquisition of electrons (reduction) or the loss of electrons (oxidation). This transfer system is an reduction-oxidation system, or redox. (Red. - Oxid. n+ = ne—, where n is number of electrons involved), and can be used to measure and... 

Thus, the peak separation can be used to determine the number of electrons transferred, and as a criterion for a Nemstian behavior. Accordingly, a fast one-electron process exhibits a AEp of about 59 mV Both the cathodic and anodic peak potentials are independent of die scan rate. It is possible to relate the half-peak potential (Ep/2. where the current is half of the peak current) to the polarographic half-wave potential, El/2 ... 

Example 2-2 The following cyclic voltammogram was recorded for a reversible couple Calculate the number of electrons transferred and the formal potential for the couple. 

K.23 A mixture of 5.00 g of Cr(N03)2 and 6.00 g of C11SO4 is dissolved in sufficient water to make 250.0 mL of solution, where the cations react. In the reaction, copper metal is formed and each chromium ion loses one electron, (a) Write the net ionic equation, (b) What is the number of electrons transferred in the balanced equation written with the smallest whole-... 

Step 2 From the half-reactions note n = 1 the number of electrons transferred. 

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